1. Field of the Invention
This invention relates to endoscopic surgical devices. More particularly, this invention relates to an endoscopic surgical instrument having bipolar electrocautery grasping end effectors. The surgical instrument of the invention has particular application as a probe which extends through a suction-irrigation cautery instrument as set forth in Ser. No. 07/959,280.
2. State of the Art
Endoscopic surgery is widely practiced throughout the world today and its acceptance is growing rapidly. In general, endoscopic surgery involves one or more incisions made by trocars where trocar tubes are left in place so that endoscopic surgical instruments may be inserted through the tubes. A camera or other optical instrument is often inserted through one trocar tube, while a cutter, dissector, or other surgical instrument is inserted through another trocar tube for purposes of manipulating and/or cutting the internal organ. Sometimes it is desirable to have several trocar tubes in place at once in order to receive several surgical instruments. In this manner, organ or tissue may be grasped with one surgical instrument, and simultaneously may be cut with another surgical instrument; all under view of the surgeon.
Various types of endoscopic surgical instruments are known in the art. These instruments generally comprise a slender tube containing a push rod which is axially movable within the tube by means of a handle or trigger-like actuating means. An end effector is provided at the distal end of the tube and is coupled to the push rod by means of a clevis so that axial movement of the push rod is translated to rotational or pivotal movement of the end effector. End effectors may take the form of scissors, grippers, cutting jaws, forceps, and the like.
Modern endoscopic procedures often involve the use of electrocautery. Indeed, several types of electrocautery devices for use in endoscopic surgery are described in the prior art. U.S. Pat. No. 4,418,692 to Guay, for example, discloses a device for use in laparoscopic tubal cauterization for blocking the fallopian tubes of a patient. The device comprises a substantially tubular body member having a spring-biased piston slidably mounted therein. A pair of electrodes (either monopolar or bipolar) are disposed to grasp living tissue when the piston is in a first position biased by the spring and to release: the tissue when a button is pressed which moves the piston into a second position. The device includes a circuit breaker which interrupts current flowing to the electrodes when the piston is in the second position. When the electrodes grasp the tissue, current is supplied to the surface of the electrode. Guay teaches two types of grasping electrodes: a springy tweezer-like electrode pair; and a sliding J-hook type electrode.
Another electrosurgical instrument for use in combination with an endoscope is disclosed in U.S. Pat. No. 5,007,908 to Rydell for "Electrosurgical Instrument Having Needle Cutting Electrode and Spot-Coag Electrode". Rydell's device includes an elongated flexible tubular member with a plurality of lumens. The distal end of the tubular member is provided with a bullet shaped ceramic tip covered with a conductive layer and having an opening coupled to a first one of the lumens. The conductive layer is coupled to a conductor which extends through a second one of the lumens to an electrical source. A second conductor, also coupled to the electrical source is slidable through the first lumen by a plunger. The two electrodes form a bipolar pair. In a second embodiment, the conductive layer on the ceramic tip is split by an insulating gap and both halves of the tip form a bipolar pair of electrodes. Rydell's device does not provide any grasping capability.
Other electrocautery probes for use with an endoscope are disclosed in U.S. Pat. No. 3,920,021 to Hiltebrandt. Hiltebrandt discloses several types of probes similar to Rydell's in that they have a substantially bullet shaped tip with hemispheric or annular conductors forming electrode pairs. Hiltebrandt also shows electrodes similar to Guay's, a pair of springy arms slidable through a tube member to grasp and release tissue. Of course, the gripping force obtainable by either Guay's B or Hiltebrandt's probes is severely limited because the electrodes must be "springy".
A bipolar electrocautery endoscopic scissors sold by Everest Medical is also known in the art and generally comprises a first fixed scissor element which is coupled to an outer tube, and a second rotating scissor element which is coupled to a push rod. The scissor elements are insulated from each other by use of ceramic layers glued to the faces of the scissors, and by an insulated pin around which the scissor element extend. Likewise, the outer tube which is connected to a first electrode wire, and the push rod which is coupled to a second electrode wire are insulated from each other, and the outer tube and push rod are coupled to a handle and actuator which effect movement of the push rod relative to the outer tube. While the Everest Medical bipolar electrocautery scissors provides the basics of a bipolar electrocautery endoscopic instrument, it has several drawbacks. In particular, the connection between the electrodes and the outer tube and push rod are by wires which are forced distally in between a ferrule and the push rod, and between an insulator on the push rod and the outer tube. This electrical connection is undesirable, however, as when the push rod and outer tube are rotated relative to the handle, electrical connection may not be properly maintained, and/or the wire contacting the outer tube may work its way proximally and end up contacting an uninsulated portion of the push rod, thereby establishing a short circuit. Moreover, because of the location of the outer tube electrode wire between the push rod and the outer tube, electrical arching is possible which could result in a short circuit between the electrodes.